1- Inteview your target market
2-Ask them if your solution solves a problem for them
3- Ask them if it is easy to switch to your solution
4-Ask them if they would pay for your solution
5-There is a formal way to do this, you form hypothesis on what you think is true and then try to gather data that proves the hypothesis it disproves the hypothesis
6-If yours is a consumer idea at least interview 100 potential customers, if yours is a B2B idea then interview at least 30 potential customers
7- If you join an incubator those guys will help you do this in a much more formal way, you need to do this every week and then come back and report the results to the team, they will in turn grill you on your results and beat you down
It is tough because it is your baby and you cannot handle when someone calls your baby ugly, but worth doing it. You are better off learning that your idea was not good early on rather than after spending a few years on it.
This is how you validate your idea.
Also check out my book Puga Sankara's Supply Chain Blog - that is a must read before spending Hundreds & Thousands of $$$ on your MBA or Masters Degree to get the best ROI or before starting your Entrepreneurial journey.